Effects of breathing air at 4 atm abs: evidence for a change in strategy

The effect of breathing air at 4 atm abs on two tasks was investigated. For the recognition memory task, subjects learned a list of symbols in anticip ation of a recognition test. The second task was a speed test in which subj ects were instructed to detect all occurrences of a given target. A signal detection analysis of performance to the recognition test showed that sensi tivity index was invariant, but the criterion (beta) became stricter under hyperbaric pressure. For the speed test, the results showed that under pres sure the error rate increased progressively with time while the working spe ed remained constant. It is argued that strategic variables may be particul arly sensitive to the hyperbaric environment.